Inventory storage and retrieval system and method with guidance for load-handling vehicle

ABSTRACT

An inventory storage and retrieval system and method are provided for a shipping or storage facility. In an embodiment, the system includes: (a) a mobile computer and radio on a load-handing vehicle; (b) sensors on the vehicle to determine the ground location and orientation of the vehicle; (c) encoders that determine the position of a lifting mechanism relative to a chassis of the vehicle; and (d) a base computer and radio that communicates with the vehicle. The system maintains an inventory database of items and their respective storage locations in three dimensions as a result of the loading activity of the vehicle. The data can be used to guide the vehicle for ground movement generally to a storage location, appropriately orient the vehicle, and then to move the lifting mechanism of the vehicle to deposit or retrieve the item at a particular storage location.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This patent application is a continuation-in-part of copending U.S.patent application Ser. No. 10/298,487, filed Nov. 18, 2002, and thispatent application claims the benefit of U.S. Provisional PatentApplication No. 60/487,436 filed Jul. 15, 2003.

FIELD OF THE INVENTION

This invention generally pertains to vehicle guidance systems and moreparticularly relates to a system for guiding a vehicle to deposit andretrieve items in conjunction with inventory tracking data.

BACKGROUND OF THE INVENTION

A guidance system for a gantry crane is disclosed in U.S. patentapplication Ser. No. 10/298,487, incorporated herein by reference in itsentirety. The guidance system of that application uses GPS technology todetermine the ground position and orientation of a gantry crane, therebyproviding directional data useful for automatically or manually drivinga vehicle such as a gantry crane to a desired location.

Various load handling systems are known, such as those disclosed in U.S.Pat. Nos. 5,512,902, 6,266,008, and 6,577,921, and in InternationalPublication No. 98/34127.

A need exists for an improved system and method for utilizing a guidedvehicle to handle items in an inventory.

BRIEF SUMMARY OF THE INVENTION

The present application relates to an inventory storage and retrievalsystem that utilizes one or more coordinate systems for tracking storagelocations and items associated with those locations. The locationinformation is used to guide a load-handling vehicle to a particularitem. Moreover, the location information is used to manage inventorydata that is updated as items are deposited or retrieved from thelocations with the vehicle.

The system manages an inventory of items respectively stored atpredetermined positions within a storage facility defined bythree-dimensional coordinates. The system keeps track of the location ofeach item with such coordinates. The location information may be used toguide a load-handling vehicle for depositing and retrieving the items.The system is particularly useful for managing and moving shippingcontainers stored in a stacked manner within a shipping facility,wherein the loading vehicle is a land-traveling unit (e.g., a gantrycrane, packer, side loader, forklift, etc.) or a rail-traveling unit.

To track the inventory, the system uses a combination of GPS and othersensor technology on the load handing vehicle to assist in guiding thevehicle to an appropriate ground position and to allow precisepositioning of a vertically-movable lifting member of the vehicle, forexample a grappler or spreader of a gantry crane, or an extendiblegrappler of a side-loader style vehicle. According to variousembodiments, the system is programmed to supplement the GPS positiondata with predetermined parameters (fixed dimensions of the vehicle,etc.) as well as encoder data that reflects the position of the liftingdevice on the vehicle, resulting in an accurate grappler and containerposition. Of course, the system may be adapted for various types ofload-handling vehicles, which may have different types of encoderdevices.

More specifically, the GPS data represents a position of a GPS receivermounted to a fixed point on a main portion of the loading vehicle (e.g.,the GPS receiver may be mounted to a beam or cab of a gantry crane).However, the true position of an item held by the loading vehicle isdetermined by the position of a lifting device of the vehicle. Thelifting device is movable relative to a main portion or chassis of thevehicle. Encoders are used to determine the position of the liftingdevice relative to the main portion of the vehicle. Separate encodersare provided for each degree of freedom. For example, in a side loaderor packer, in which the lifting device is vertically movable relative tothe main portion, the encoder determines a supplemental Z distance ofthe lifting device relative to the GPS receiver(s). In a vehicle whereinthe lifting device is movable in a side-to-side and/or front-to-reardirection, respective encoders are provided to measure supplemental Xand Y distances of the lifting device with respect to a predeterminedpoint, such as the GPS receiver(s). The encoders may be any appropriatetype of encoder or sensor for example, mechanical, magnetic, or optical.These encoders can, for example, measure the degree of actuation of acylinder or a feed distance of a cable.

In an embodiment, another factor in determining the actual position ofan item is data representing the orientation of the loading vehicle.Based on the vehicle orientation, the system adjusts for knownstructural parameters of the loading vehicle to determine the positionof the item with respect to the GPS receiver(s). For example, in asystem wherein the lifting device is mounted on a particular side of thevehicle, the lifting device may be at a fixed horizontal positionrelative to the GPS receiver(s), and the orientation information permitsthe system to determine the precise position of the lifting device (andtherefore a container) with respect to the ground. Orientationinformation may be determined by the use of multiple, horizontallyspaced GPS receivers. Alternatively, orientation information may bedetermined by other appropriate means, such as a compass, gyroscope,particularly in a system wherein the vehicle includes a single GPSreceiver. Orientation data may be unnecessary in a system wherein theorientation of the vehicle is known, such as for certain loadingvehicles maintains a fixed orientation with respect to rails.

In an embodiment, the system keeps track of whether an item is in astationary mode for storage or in transit. For example, the systemdetermines whether a container is “unlatched” or “latched” with respectto a grappler of the loading vehicle. While the container is“unlatched,” the system stores a record of the position of thecontainer, which remains stationary at a position last deposited(switched from “latched” to “unlatched”) by the vehicle. If thecontainer is “latched,” the position of the container is being moved toa destination location, and the system stores an updated position forthe container where it is deposited at the moment it is “unlatched” fromthe loading vehicle.

Various configurations are possible, such as those described in thefollowing examples.

In a system used with a loading vehicle having a land-travelingtraveling configuration, at least one GPS receiver can be used to trackpositions along two dimensions (e.g., X and Y). Other encoders orsensors are implemented to supplement the GPS data to reflect theposition of the lifting device relative to the GPS receiver. Forexample, an encoder can be used to determine position in a heightdimension (Z). The system determines orientation, such as by therelative positions of multiple GPS receivers or through a dedicatedorientation sensor (compass, etc.).

Where the loading vehicle is a rail-traveling unit, a GPS receiver needsonly to track positions along one dimension (e.g. X), because the railis fixed in a known position.

The hardware includes at least one GPS antenna and receiver, wirelessradio, electronic controller, on board server, and ground station. Thesoftware enables the operation of the hardware for purposes of positionand control. The software may include operating programs, utilityprograms, conversion programs, and language processors includingcompilers, assemblers, and translators.

The system generates an output that indicates a position relative to alocal coordinate system based on a “Latch” or “Unlatch” activity:

X position 6 places in tenths of feet Y position 4 places in tenths offeet Z position 4 places in tenths of feet

In an embodiment, a variation of the system uses the container locationcoordinates for guiding movement of the loading vehicle.

In an embodiment, an advantage of the present invention is that itprovides an improved system and method for tracking an inventory.

A further advantage of the present invention is that it provides animproved system and method for guiding load-handling vehicles in anenvironment with tracked items.

Yet another advantage of the present invention is that it provides anaccurate system and method of determining a location of a lifting deviceof a load-handling vehicle.

These and other advantages of the invention will be apparent from thedescription of the invention provided herein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a load-handling vehicle on the ground withrelation to a base station and a plurality of orbiting globalpositioning satellites.

FIG. 2 is a rear elevation of a rubber tire gantry crane suitable foruse a load-handling vehicle according to teachings of the presentinvention.

FIG. 3 is a side elevation of a side loader suitable for use as aload-handling vehicle according to teachings of the present invention.

FIG. 4 is a flow chart illustrating an exemplary process for managing aninventory according to teachings of the present invention.

FIG. 5 is a schematic diagram of a system according to teachings of thepresent invention.

FIG. 6 is a schematic plan view of a vehicle approaching an item to beretrieved, the crane having present vehicle orientation Φ_(VP) thatmatches a desired vehicle orientation Φ_(VD).

FIG. 7 is a schematic plan view of a vehicle parked at a desired groundposition wherein the lifting mechanism must be moved a lateral distanceΔL to latch the item located at the actual storage location positionX_(S1), Y_(S1), Z_(S1).

DETAILED DESCRIPTION OF THE INVENTION

The following examples further illustrate the invention but, of course,should not be construed as in any way limiting its scope.

Referring to FIG. 1, a storage facility is illustrated having a basestation 100, at least one load-handling vehicle 200 that travels on theground, and a plurality of items 30 located at various storage locationsin the facility. A three-dimensional matrix is used for determining thelocations of the vehicle 200 and items relative to axes X, Y, and Z. Forexample, as shown in FIG. 1, an actual storage location of an item isindicated as X_(S), Y_(S), Z_(S), and a present ground position of thevehicle is X_(VP), Y_(VP), Z_(VP). A plurality of orbiting globalpositioning satellites 40 is illustrated.

The vehicle 200 has a movable lifting device 250 that is configured tolift at least one of the items 30. The items 30 illustrated herein arestandard shipping containers of a generally known type, which havelatching structures located at the respective upper corners of eachcontainer. The lifting device 250 includes four twistlocks operable toselectively latch and unlatch the item 30. The invention herein will bedescribed to the illustrated example, however, it will be understoodthat the invention may be used with an inventory of any type ofcorresponding vehicle, lifting device, and item. For example, in variousembodiments, the lifting device may a spreader for lifting an item suchas a truck trailer, or the vehicle could be a forklift. Those skilled inthe art will also recognize that the items 30 may be placed in storagelocations on the ground, stacked on top of each other, or verticallyarranged on racks or shelves.

To demonstrate the versatility of the invention to various environments,the figures herein illustrate load-handling vehicles having differentconfigurations. For example, FIG. 2 illustrates a load-handling vehicle200A configured as a rubber tire gantry crane, and FIG. 3 illustrates aload-handling vehicle 200B in a configuration known as a side loader.

The gantry crane vehicle 200A of FIG. 2 includes a frame or chassiscomprising vertical columns 202 connected by horizontal beams 204. Thechassis is mounted on wheels 206 operable to drive and maneuver thevehicle 200A on the ground. The vehicle 200A includes a lifting device250A configured as a grappler for lifting standard shipping containers.The exemplary vehicle 200A includes a vertically-movable stabilizer beam206. The lifting device 250A is suspended from the stabilizer beam 208by a trolley 210 that is mounted for horizontal movement transverselyalong the stabilizer beam 208. As a result, the lifting device 250A ismovable relative to the chassis in horizontal and vertical directions.

The side loader vehicle 200B of FIG. 3 includes a chassis 260 that isequipped with wheels 262 for driving and maneuvering the vehicle on theground. The vehicle 200B also includes a lifting device 250B mounted ona boom 264. As illustrated, the lifting device 250B is configured tolatch standard shipping containers. The boom 264 is pivotally andtelescopically movable for adjusting the vertical and horizontalposition of the lifting device 250B relative to the chassis 260. Moreparticularly, the boom 264 includes a first boom portion 264A that ispivotally mounted to the chassis 260 at a trunnion 265 and a second boomportion 264B that is telescopically extendible from the first boomportion 264A. At least one linear actuator 266 is provided for actuatingpivotal motion of the first boom portion 264A. A linear actuator (notshown) is also provided for extending the second boom portion 264Brelative to the first boom portion 264A.

According to an aspect of the present invention, an inventory databaseis maintained by tracking the locations of items moved by theload-handling vehicle. The load-handling vehicle utilizes a combinationof GPS and other sensor technology to provide precise position of thelifting device within a three dimensional matrix defined by X, Y, and Zcoordinates of a storage area or facility. More particularly, one ormore GPS receivers detect a general position of the vehicle, and theposition of the lifting device is determined by detecting the currentposition of lifting device on vehicle and supplementing the generalvehicle location to reflect the position of the lifting device positionon the vehicle. The GPS data is also used for guiding the vehicle tomaneuver to a desired location. The vehicle has a mobile computer thatcommunicates via RF with a base computer at the base station whichupdates the database pursuant to loading and unloading activity.Accordingly, the database stores current information reflecting the X,Y, and Z storage location coordinates of items stored at the facility,which location information may be used to accurately guide the vehicleto retrieve or deposit selected items. In an embodiment, the databasefurther stores identification data that is unique per each of the items.Also, in an embodiment, the database also stores orientation data usefulto guide the vehicle to approach the storage location from anappropriate direction.

Referring to FIG. 5, a system is illustrated in which the base station100 is equipped with a base computer 112 that has access to an inventorydatabase 114. A two way radio, referred to herein as transceiver 116,and corresponding antenna 118 is provided through which the basecomputer 112 sends and receives RF signals. In an embodiment, a GPSreceiver 120 and corresponding GPS antenna 122 are provided at the basestation 100 to provide a reference GPS signal to the base computer 112.

At the left side of FIG. 5 is a schematic diagram of components carriedon the vehicle 200. The load-handling vehicle is equipped with at leastone mobile GPS receiver 220 having a corresponding GPS antenna 222. Thevehicle 200 includes a mobile computer 212 that receives signals fromthe GPS receiver 220. Additionally, the vehicle includes a mobiletwo-way radio transceiver 216 through which the mobile computer sendsand receives RF signals at a frequency corresponding to the basetransceiver 116. The base and mobile radio transceivers 116, 216facilitate communication between the base computer 112 and mobilecomputer 212 as the vehicle 200 maneuvers around the facility. Toillustrate possible mounting locations for the GPS antenna 222, FIG. 2,for example, illustrates the vehicle 200A having a GPS antenna 222mounted on top of the upper horizontal beam 204, and the vehicle 200B ofFIG. 3 has a GPS antenna 222 mounted on top of a rearward portion of thechassis 260. The GPS antennae 122, 222 can be mounted in any positionthat affords suitable skyward exposure for reception from the GPSsatellites 40 (FIG. 1).

The GPS data represents a position of the GPS antenna. The liftingdevice is movable relative to the main portion of the vehicle supportedon the ground. Where the GPS antenna is mounted to the main portion ofthe vehicle, as in the illustrated embodiments, the GPS antenna does notindicate a precise location of the lifting device, because the liftingdevice is movable relative to the GPS antenna. In order to determine theprecise position of the lifting device and an item held by the liftingdevice, the vehicle is also equipped with encoders that detect theposition of the lifting device relative to a frame or chassis of thevehicle. The position of the lifting device (and an item held by liftingdevice) is determined by adjusting the GPS position to compensate forthe position of the lifting device relative to the GPS antenna.

More specifically, as illustrated in FIG. 5, the vehicle 200 is equippedwith one or more encoders 218A, 218B to measure movement of the liftingdevice and to provide a corresponding signal to the mobile computer 212,which determines the movement or position of the lifting device relativeto the main portion of the vehicle.

Preferably separate encoders are provided for each degree of freedom ofthe lifting device. Separate encoders are provided for each degree offreedom. In an embodiment wherein the vehicle is a forklift type of sideloader or packer, wherein the lifting device is vertically movable alongthe Z axis relative to the main portion, a single encoder may besufficient for determining a supplemental Z distance of the liftingdevice relative to the GPS receiver. In a vehicle wherein the liftingdevice is movable in a side-to-side and/or front-to-rear direction,respective encoders are provided to measure supplemental X and Ydistances of the lifting device with respect to the GPS receiver(s). Theencoders may be any appropriate type of encoder or sensor for example,mechanical, magnetic, or optical, as are generally known. These encoderscan, for example, measure the length of actuation of a cylinder, a feeddistance of a cable, a degree of rotation of a hoist drum for coiling acable, or an angle of a pivotal joint, or the degree of movement betweenany relatively movable structures.

In the vehicle 200A shown in FIG. 2, the vehicle is equipped with afirst encoder (see 218A in FIG. 5) for measuring the horizontal positionof the trolley 210 relative to the stabilizer beam 210 and a secondencoder (see 218B in FIG. 5) for measuring a vertical position of thestabilizer beam relative to the columns 202. In the vehicle 200B of FIG.3, a first encoder (see 218A in FIG. 5) measures an angle of the firstboom portion 264A that is pivotally mounted to the chassis 260, and asecond encoder (see 218B in FIG. 5) for measuring a relative slidableposition of the telescoping second boom portion 264B relative to thefirst boom portion 264A.

One or more encoders 218A, 218B (FIG. 5) measure movement of the liftingdevice and provide a corresponding signal to the mobile computer 212,which determines the movement or position of the lifting device relativeto the main portion of the vehicle. Separate encoders are provided foreach degree of freedom. For example, in an embodiment wherein thevehicle is a forklift type of side loader or packer, wherein the liftingdevice is vertically movable relative to the main portion, the encoderdetermines a supplemental Z distance of the lifting device relative tothe GPS receiver(s). In a vehicle wherein the lifting device is movablein a side-to-side and/or front-to-rear direction, respective encodersare provided to measure supplemental X and Y distances of the liftingdevice with respect to the GPS receiver(s). The encoders may be anyappropriate type of encoder or sensor for example, mechanical, magnetic,or optical, as are generally known. These encoders can, for example,measure the degree of actuation of a cylinder or a feed distance of acable.

Referring again to FIG. 5, in an embodiment wherein the GPS receiver 120and corresponding antenna 122 are located at the base station 100, thesignal from the base GPS receiver 120 is sent to the base computer 112to be used as a reference calibration that can be used to more preciselydetermine the position of the vehicle 200. In particular, the basecomputer 112 can be programmed to compare the currently measuredposition of the antenna of the base GPS receiver 120 to a known, fixedreference position of the antenna 122, from which a vector can becalculated to represent the difference between the known and measuredpositions. Assuming that a similar difference between measured andactual positions currently affects the mobile GPS receivers 220, thevector is applied to correct the position measured by the mobile GPSreceivers 220 for improved precision.

FIG. 4 is a flow chart illustrating an exemplary process 400 formanaging an inventory according to teachings of the present invention.Generally, steps of the process 400 result in moving an item from afirst storage location X_(S1) Y_(S1) Z_(S1) to a second storage locationX_(S2) Y_(S2) Z_(S2).

At step 405, item identification information and an actual storagelocation X_(S1) Y_(S1) Z_(S1) are transmitted to the vehicle. Withreference to FIG. 5, the item identification and actual storage locationinformation are input to the base computer 112 and transmitted via an RFsignal from base transceiver 116. The base computer 112 obtains the itemidentification and actual storage location data from the inventorydatabase 112 or by user input. The data is received by the mobiletransceiver 216 on board the vehicle 200 and is sent to the mobilecomputer 212. Alternatively, the item identification and storagelocation X_(S1) Y_(S1) Z_(S1) could be entered into the mobile computerby an operator of the vehicle.

As indicated at step 410 of FIG. 4, a present ground location X_(VP)Y_(VP) is detected, and in an embodiment, a present orientation Φ_(VP)of the vehicle is additionally detected. As discussed above, inconnection with FIG. 5, the present ground location of the vehicle ispreferably determined using a GPS signal received from the GPS receiver220 and antenna 222 on the vehicle 200. In an embodiment, another factorin determining the position of an item is data representing theorientation of the loading vehicle. The present orientation of thevehicle can be determined using various techniques. For example, thevehicle may be equipped with a second GPS receiver 220 having an antenna222 mounted in a laterally spaced relation from the first GPS antenna.

The present ground position of the vehicle X_(VP) Y_(VP) may be thecurrent X, Y position of one of the mobile GPS antennas 222, asillustrated in the examples of FIGS. 2 and 3. However, those of ordinaryskill in the art will recognize the possible convenience of adjustingthe GPS position by known values particular to the vehicle so that thepresent ground position X_(VP) Y_(VP) represents a different point onthe vehicle such as the geometric center of the vehicle or any otherpoint. For example, with reference to FIG. 7, the present groundlocation of the vehicle X_(VP) Y_(VP) is defined at the center of thevehicle 200A. The mobile computer 212 (FIG. 5) determines the centerX_(VP) Y_(VP) based on predetermined dimensions of the vehicle and itsorientation Φ_(VP) by adjusting the GPS coordinates of the GPS receiverby a corresponding vector.

The present orientation Φ_(VP) of the vehicle can be determined invarious ways. In an embodiment wherein the vehicle is equipped withmultiple GPS receivers 220, the mobile computer 212 can calculate theorientation of the vehicle based on the different positions sensed bythe first and second GPS receivers 220. Alternatively, the presentvehicle orientation Φ_(VP) may be determined by other appropriate means,such as a compass, gyroscope, or another suitable directionaltransducer, particularly in a system wherein the vehicle includes asingle GPS receiver.

Referring back to FIG. 4, step 415 optionally calculates a desiredground location X_(VD1), Y_(VD1) of the vehicle that is offset from theground storage location X_(S1), Y_(S1). The desired offset positionX_(VD1), Y_(VD1) depends on the type of vehicle, lifting device andcorresponding item being lifted. For example, the side loader stylevehicle 200B to FIG. 3 needs to be parked at a laterally offset positionbeside a container storage location in order to properly position thelifting device 250B to meet the top of the item 30. In FIG. 3, forexample, the offset is indicated as ΔX, as the vehicle happens to bealigned on the X axis as illustrated. Referring to FIG. 7, the offset isindicated as ΔL, which has components ΔX and ΔY along the X and Y axes.In FIG. 7, the desired offset is laterally under the gantry stylevehicle 200A in order to allow the vehicle to concurrently straddlemultiple stacks of items.

In step 415, a desired orientation is also calculated. In an embodiment,it is desirable for the vehicle to approach the item storage locationfrom a particular angle or orientation. The approach orientation can benecessary for access to the item, depending on the configuration of thevehicle with respect to the item 30 and the available free areas onpavement near the item. For example, with respect to FIG. 6, it isdesirable for the vehicle 200A to be aligned at a vehicle orientationΦ_(VP) to approach the item 30 along the orientation Φ_(VD) of the item30. In FIG. 6, the vehicle 200A is a gantry crane, and the item is ashipping container. Because this vehicle 200A must straddle the item 30in order to land the lifting device on the container, it is desirablethat the vehicle approaches the item from an orientation alignedlongitudinally with the item 30. In a situation wherein the side loadervehicle 200B is used, the desired orientation Φ_(VD) of the item 30would be perpendicular the orientation illustrated in FIG. 6, becausethe side loader is structurally configured to lift a shipping containerfrom the side. Orientation data may be unnecessary in a system whereinthe orientation of the vehicle is constant, such as for loading vehiclesthat move on rails or in manual systems wherein the final approachrelies upon the judgment of the driver as to the best approachdirection. The desired orientation Φ_(VD) can be calculated by the basecomputer 112 or the mobile computer according to stored parameters,including the storage orientation of the device, the vehicleconfiguration, predetermined pathways between obstacles or multipleitems.

In FIG. 4, reference numeral 420 indicates the step of maneuvering thevehicle to the desired location and orientation that were calculated instep 415. When the vehicle is at the desired location, the groundposition and orientation of the vehicle X_(VP), Y_(VP), Φ_(VP) match,within an appropriate range of tolerance, the desired ground positionand orientation of the vehicle X_(VD1), Y_(VD1), Φ_(VD1). According tovarious embodiments, the maneuvering step 420 can be automatic, manual,or a combination of manual and automatic maneuvering. For example, thevehicle can be equipped with a guidance indicator 226 (FIG. 5) todisplay directions to a human operator for driving and steering thevehicle 200 to the desired location. Optionally, the vehicle 200 isequipped with guidance actuator 228 (FIG. 5) that is adapted to controlthe drive and steering of the vehicle automatically to the desiredground location at the desired orientation.

When the vehicle has arrived at the desired ground position, the liftingdevice is then moved to the storage location X_(S1), Y_(S1), Z_(S1), asindicated at step 425 of FIG. 4. For example, with respect to the gantrycrane style vehicle 200A of FIG. 2, the lifting device may be moved tothe storage location by moving the trolley 210 and stabilizer beams 208as necessary to vary the position of the suspended grappler or liftingdevice 250A. As FIG. 7 schematically illustrates, the lifting devicewould have to be moved laterally a distance of ΔL in order to beproperly positioned to land on top of the container 30. On the sideloader style vehicle 200B of FIG. 3, the lifting device is moved byadjusting the angle and telescoping length of the boom 264. Notably, thelifting device must be moved to an appropriate vertical position on theZ axis according to the height of an item 30 or according to thevertical position of an item that sits on a stack or which resides in arack in a stacked relation to other items. When the lifting device 250is properly positioned relative to the item 30 to be lifted, the liftingdevice is latched to the item as indicated at step 430 in FIG. 4. Wherethe lifting device 250 is a grappler, as in the illustrated examples,the twistlocks are rotated to the latched position within thereceptacles of the container.

In an embodiment, the system keeps track of whether an item is in astationary mode for storage or in transit. For example, the systemdetermines whether a container is “unlatched” or “latched” with respectto a grappler of the loading vehicle. A signal associated with anactuator of the latches or a latch sensor may be used to provide acorresponding signal, as will be recognized by those skilled in the art.Preferably, as indicated at step 435 of FIG. 4, the mobile computer 212signals the base computer 112 to indicate that the represents that theitem 30 is “in transit” due to the latched condition of the liftingdevice, and it is assumed that the position of the item 30 can betracked along with the present location of the vehicle. The basecomputer 112 preferably updates the database to reflect that theparticular item 30 is no longer located at its storage location X_(S1),Y_(S1), Z_(S1) and that it is now carried by the vehicle. If thecontainer is latched, the position of the container is being moved to adestination location, and the system stores an updated position for thecontainer where it is deposited at the moment it is “unlatched” from theloading vehicle.

As indicated at step 440, a new storage location X_(S2), Y_(S2). Z_(S2),is provided to the mobile computer 212 to which the item is to be movedand deposited. The storage location X_(S2), Y_(S2) Z_(S2) can betransmitted to the mobile computer 212 from the base computer 112 at thebase station 100, or alternatively, the storage location storagelocation X_(S2), Y_(S2), Z_(S2), could be input by an operator aboardthe vehicle.

At step 445, the present vehicle ground location X_(VP) Y_(VP) of thevehicle is determined in a manner as discussed above in connection withstep 410. By periodically updating the present ground location X_(VP)Y_(VP), the vehicle is tracked by the mobile computer 212 and/or thebase computer 112. At step 450, a desired offset ground locationX_(VD2), Y_(VD2) of the vehicle is calculated relative to the storagelocation X_(S2), Y_(S2), Z_(S2) in the manner discussed above inconnection with step 415.

As indicated at step 455, the vehicle is maneuvered to the desiredlocation so that the present vehicle position X_(VP) Y_(VP) matches thedesired vehicle position X_(VD2), Y_(VD2), within a suitable range oftolerance, as discussed above in connection with step 420. Themaneuvering step 455 may be manually directed by the operator with theassistance of the guidance indicator 226 (FIG. 5), or the maneuveringmay be partially or fully automated with the assistance of the guidanceactuator 228 (FIG. 5).

When the vehicle is parked at the desired vehicle ground location,X_(VD2), Y_(VD2), the lifting device is moved to place the item 30 atrest at the desired storage location X_(S2), Y_(S2), Z_(S2). Thisrequires movement of the lifting device as discussed above in connectionwith step 425. When the item is properly positioned, the lifting device250 is unlatched from the item 30, as indicated by step 465. Forexample, in the example wherein the lifting device is a grappler, asillustrated in FIGS. 2 and 3, the twistlocks are moved to an unlatchedposition to release the grappler from the container. The mobile computer212 transmits a signal to the base computer 112 that the item 30 hasbeen unlatched, and accordingly, the base computer 112 updates thedatabase to reflect that the particular item corresponds to the newstorage location X_(S2), Y_(S2), Z_(S2) where it was just deposited.While the container is “unlatched,” the system stores a record of theposition of the container, which remains stationary at a position lastdeposited (switched from “latched” to “unlatched”) by the vehicle.

All references, including publications, patent applications, andpatents, cited herein are hereby incorporated by reference to the sameextent as if each reference were individually and specifically indicatedto be incorporated by reference and were set forth in its entiretyherein.

The use of the terms “a” and “an” and “the” and similar referents in thecontext of describing the invention (especially in the context of thefollowing claims) are to be construed to cover both the singular and theplural, unless otherwise indicated herein or clearly contradicted bycontext. Recitation of ranges of values herein are merely intended toserve as a shorthand method of referring individually to each separatevalue falling within the range, unless otherwise indicated herein, andeach separate value is incorporated into the specification as if it wereindividually recited herein. All methods described herein can beperformed in any suitable order unless otherwise indicated herein orotherwise clearly contradicted by context. The use of any and allexamples, or exemplary language (e.g., “such as”) provided herein, isintended merely to better illuminate the invention and does not pose alimitation on the scope of the invention unless otherwise claimed. Nolanguage in the specification should be construed as indicating anynon-claimed element as essential to the practice of the invention.

Preferred embodiments of this invention are described herein, includingthe best mode known to the inventors for carrying out the invention. Itshould be understood that the illustrated embodiments are exemplaryonly, and should not be taken as limiting the scope of the invention.

1. A method for managing an inventory comprising: providing a databasestoring item identification information for a plurality of respectiveitems and three dimensional storage location for each of the respectiveitems; transmitting the storage location information and the itemidentification information to a vehicle having a lifting mechanismoperable to selectively handle at least one of the items; determining adesired position and orientation of the vehicle to provide access to thestorage location; detecting a present ground position of the vehicle;detecting an orientation of the vehicle; comparing the present groundposition and orientation information to the desired ground position andorientation information; automatically steering the vehicle along adesired land travel path that can include at least one curved portion sothat the present position and orientation matches the desired groundposition and orientation information; detecting a vertical position ofthe lifting mechanism; moving the lifting mechanism of the vehicle to avertical coordinate and horizontal coordinates associated with thestorage location; and updating the database to reflect changes to theitem identification information and location information to reflectretrieval or deposit of an item from the storage location.
 2. The methodof claim 1, wherein the desired ground position is the storage location.3. The method of claim 1, further comprising the step of calculating adesired ground position of the vehicle that is offset from the storagelocation such that the lifting mechanism of the vehicle is positioned toreach the storage location when the vehicle is at the desired groundposition.
 4. The method of claim 1, wherein the storage locationinformation includes orientation information used to determine a desiredorientation of the vehicle that permits access to the storage location.5. The method of claim 1, wherein the step of detecting a groundposition includes receiving a GPS signal.
 6. The method of claim 1,whereby said retrieval or deposit operation is determined by arespective unlatching or latching of the lifting mechanism with respectto the respective item.
 7. The method of claim 1, whereby the liftingmechanism is selectively operable in a secured mode in which the liftingmechanism is secured to the item and a free mode in which the liftingmechanism is free from the item, and whereby the method furthercomprises transmitting a signal indicating whether the lifting mechanismis in the secured mode.
 8. The method of claim 7, whereby the updatingstep includes storing assigning location information to an item at alocation at which the item is released from the lifting mechanism.